The present invention relates generally to the field of firefighting vehicles which are configured to pump or otherwise deliver a firefighting agent or suppressant (e.g., water, foam, etc.) to an area of interest. More specifically, the present applicant relates to the configuration of a pump system (e.g., a fire pump system, etc.) for a firefighting vehicle.
Firefighting vehicles come in a variety of forms. For example, certain firefighting vehicles, known as pumpers, are designed to deliver large amounts of firefighting agents, such as water, foam, or any other suitable fire suppressant to an area of interest. One or more of the firefighting agents may be retrieved from a tank carried by the firefighting vehicle and/or may be retrieved from a source external the firefighting vehicle (e.g., hydrant, pond, etc.). Other firefighting vehicles, known as tankers, are designed to hold and/or transport relatively large quantities of firefighting agents. Still other firefighting vehicles, known as aerials, are designed to additionally elevate ladders or booms. Further still, some firefighting vehicles, known as specialized firefighting vehicles, are designed for responding to unique firefighting circumstances and may be designed for delivering firefighting agents to difficult to reach locations (e.g., airport rescue, etc.).
Regardless of form, a number of firefighting vehicles include pump systems for pressurizing the firefighting agent retrieved from a tank or an external source. Typical firefighting vehicles include a single pump that operates in a relatively narrow pressure window. Because the option of hand-held hose operation is desirable, typical firefighting vehicles include a relatively low pressure pump system. Modern firefighting needs, however, sometimes require the use of multiple pumping pressure levels, combinations of agents, and a great deal of firefighting versatility. More specifically, modern firefighting needs require both the use of very high pressure output levels as well as more conventional lower pressure output levels. For example, it may be desirable to use a high pressure output level to quickly cool or extinguish a large area of fire. This high pressure output may be able to rapidly remove oxygen from the fire, thereby terminating a component of the fire's fuel. Immediately thereafter, it may then be desirable to use a lower pressure output to blanket the area with a fire suppressing foam mixture, for example. Alternatively, it may be desirable for firefighters to switch from high to low pressure flow operation in order to use hand-held nozzles and hoses. The need for firefighting versatility and substantially different fluid pressure output levels presents several design difficulties and challenges.
Some conventional firefighting vehicles only provide a low pressure fluid output. Other conventional firefighting vehicles may provide a high pressure fluid output. Those firefighting vehicles having both a high pressure output and a low pressure output often suffer from a number of problems. For example, firefighting vehicles capable of providing varying water pressure output options typically contain two substantially separate fluid delivery systems, pump systems, and/or waterways, where one system is designed for high pressure operation, and another separate system is designed for low pressure operation. Providing two separate output systems creates a number of difficulties regarding the design, manufacture, and operation of firefighting vehicles. For example, during design, providing two separate fluid delivery systems means an increase in vehicle hydraulics design complexity. In order to facilitate two separate pump systems of different pressure levels, typical firefighting vehicles may have to provide complicated and costly unclutching devices configured to remove mechanical power from a pump. In addition to specific design problems and costs, providing two separate pressure systems often duplicates many parts, generally increasing costs, weight, and power requirements. Significant weight and power increases may render a firefighting vehicle impractical for certain applications. For example, it may be desirable to air transport a firefighting vehicle to a remote location. Conventional firefighting vehicles having two separate pumping systems and/or waterways, and also having high horsepower engines to support the aforementioned systems, are too heavy for many air transport applications. Traditional air transportable firefighting vehicles, on the other hand, have been limited in function and pressure versatility. Ironically, the function and pressure versatility features of an air transportable firefighting vehicle is critical. Backup firefighting capability at a remote location may not be readily available. Furthermore, in the context of an airplane crash, a key use for air-transportable firefighting vehicles, the extreme heat of burning fuel makes rapid cooling and extinguishing via a high pressure output, followed by a low pressure foam blanketing output, for example, critical and highly desirable.